Epitaxial α-Ta (110) film on a-plane sapphire substrate for superconducting qubits on wafer scale

Abstract Realization of practical superconducting quantum computing requires many qubits of long coherence time. Compared to the commonly used Ta deposited on c-plane sapphire, which occasionally form α -Ta (111) grains and β -tantalum grains, high quality Ta (110) film can grow epitaxial on a-plane sapphire because of the atomic relationships at the interface. Well-ordered α - Ta (110) film on wafer-scale a-plane sapphire has been prepared. The film exhibits high residual resistance ratio. Transmon qubits fabricated using these film shows relaxation times exceeding 150 μ s. The results suggest Ta film on a-plane sapphire is a promising choice for long coherence time qubit on wafer scale.